There are numerous indications that between the decadence of Roman architecture and the invasion of the Moors, Spain produced a phase of architecture quite her own,[101] of which the most striking characteristic was the horseshoe arch. It has been suggested that this kind of arch was introduced from Constantinople; but students of Spanish architecture have long tried in vain to ascertain with certainty either the date of its appearance or the source of its introduction. It is known to have existed centuries before the Christian era in Persia, India, and other parts of Asia, without, however, characterising any special style of architecture. Almost until the close of the nineteenth century it was erroneously believed that the horseshoe arch entered Spain for the first time with her Moorish invaders. We now know for a certainty that Spain had it long before--that she had it already in the second century. Tombstones with Roman inscriptions have been found with horseshoe arches sculptured upon them,[102] and it has even been found sculptured on pagan tombstones whose inscriptions point unerringly to the second century.[103] As Christian architecture began to rise on Spanish soil, with it there _reappeared_ the horseshoe arch. It is visible upon the sepulchral tomb, in Mértola, of a man named Andrew, which bears these words, “_Princeps cantorum sacrosancte aeclisae Mertillane_,” and the date 525. This arch has also been found in two white marble windows, the one, now in the Museum of Merida, has barbaric ornamentations; the other, with three horseshoe arches more pronounced, exists in the church of St. Martin de Nieble.[104] A church discovered in 1789, close to the ruins of Segobriga, and which contains the epitaph of Bishop Sephronius, who died in 550, has four somewhat oval horseshoe arches in its chancel. It was thought until quite lately that there were no traces of this arch having existed in Andalusia before the arrival of the Moors, but Señor Gomez-Morenno believes he has discovered three edifices in which it was used: one of these is the western entrance of the town of Cordova, which the Moors called _Bibalatarin_. The Arab historian relates that the Visigothic nobility and garrison escaped by it in 711 A.D., to take refuge in the church of San Acisclo; and this circumstance alone is sufficient to verify its antiquity.